1. Field of the Invention
This invention relates in general to an inductive-write magnetoresistive-read horizontal head for magnetic recording, and more particularly, to a horizontal magnetic head having two polarization conductors to simultaneously disable the write head during the read back process to eliminate the secondary read back signal from the inductive-write head.
2. Description of Related Art
Magnetic heads or transducers typically employ inductive elements for recording and reading data. As is well known, magnetic heads may comprise Permalloy (NiFe) layers that provide a transducing gap at which varying flux signals result in data being recorded on a magnetic disk during the write mode. During the read mode, magnetic flux representative of the recorded signals is sensed at the transducing gap to produce electrical signals which are read out for further utilization.
In the past, magnetoresistive (MR) devices have been used as flux sensing elements to implement the readout function. In a conventional MR head, the MR element and a biasing element, which is either a conductor or a magnetic layer, are positioned in a gap formed between two flux guide elements.
In known magnetic heads, a write gap and a read gap are formed distinctly. In this configuration, a central flux guide is disposed between the read flux guide and the write flux guide and forms part of a magnetic yoke of the write portion as well as of the magnetic yoke of the read portion of the magnetic head. It is known that a write gap may function as a read gap when information is being read. This phenomenon is utilized in a structure in which information is written and read by one and the same head element which includes separate write and read gaps therein. However, in this type of write/read magnetic head, the write gap functioning as a read gap has the detrimental result that a part of the magnetic flux of the passing medium which is opposite the write gap is guided towards the magnetoresistive element via the shared central flux guide. As a result, extra magnetic pulses are introduced into the magnetoresistive element in the case of, for example, a medium comprising digital information. These pulses interfere with the magnetic pulses guided towards the magnetoresistive element via the read gap, and perturb the signal to be measured thereby detrimentally influencing the signal-to-noise ratio.
The detrimental phenomenon described above, which occurs in the known magnetic head during operation, is elucidated as follows. If it is assumed that a small magnetized area on a recording medium, for example, a magnetic tape or disk, is present just in front of the write gap. This area can be considered to be an almost ideal flux source due to the low permeability of the medium. A part of the flux, which is dependent on the distance from and the size of the write gap, will enter the write portion via the outer flux guide adjacent to the write gap and will leave the write portion via the central flux guide, or vice versa. The greater part of the magnetic flux entering the write portion returns to the contact face via the magnetic yoke of the write portion. This part of the flux subsequently traverses the sensitive magnetoresistive read element. Dependent on the direction of movement of the medium, the part of the flux traversing the magnetoresistive element gives rise to an extra pulse before or after the main pulse which results from reading said magnetized area by the magnetic head.
Moreover, when information is being written, the quantity of magnetic flux generated by the inductive element and guided towards the magnetoresistive element via the shared flux guide may be so much that the magnetoresistive element is destabilized, which may considerably reduce its sensitivity.
Attempts have been made to eliminate or minimize the contribution from the write circuit. For example, U.S. Pat. No. 5,270,895, issued Dec. 14, 1993, to Ruigrok et al., entitled "COMBINED READ/WRITE THIN-FILM MAGNETIC HEAD WITH COMPOSITE SHARED FLUX GUIDE", incorporated herein by reference, discloses a read portion including a magnetoresistive element, a write portion including an inductive element, and a shared flux guide between the read and write portions. Ruigrok separates the read and write functions by providing the shared flux guide as a sandwich structure of two soft magnetic layers separated by an insulating layer, except that the soft magnetic layers are interconnected in a magnetically conducting manner proximate to the head face. In this vertical head configuration, the secondary read back signal from the inductive-write head is not disabled, but rather is physically diverted away from the magnetoresistive element.
Another example of a read/write head which attempts to eliminate or minimize the contribution from the write circuit is disclosed in U.S. Pat. No. 5,255,141, issued Oct. 19, 1993, to Valstyn et al., entitled "READ-WRITE MAGNETIC HEAD WITH FLUX SENSING READ ELEMENT", which is incorporated herein by reference. Valstyn discloses providing a bypass around the magnetoresistive element during the write operation. The bypass is normally operable thereby bypassing the magnetoresistive element. However, during a read operation, a saturation current is applied to the magnetic valve conductor to open the shunt path thereby bypassing the magnetoresistive element. Again this is a vertical head configuration, and only one gap is provide for performing the write and read functions. Thus, a secondary read back signal form an inductive-write head is simply not present. Rather, the magnetic valve acts as a switch to allow the flux sensing element to sense signals only during read operations.
It can be seen then that there is a need for an inductive-write, magnetoresistive-read magnetic head which eliminates the secondary read back signal from the inductive-write head in head structures having both an inductive-write head and a yoke or recessed magnetoresistive-read (MR) with a shared pole.
It can also be seen that there is a need for a head structure which incorporates two polarization conductors, one to bias the magnetoresistive stripe and the second to simultaneously disable the write head during the read back process.
Still further, it can be seen that there is a need for a magnetic head structure having a shared pole design that minimizes the offset between write and read functions.